This invention relates generally to air flow sensing, and more particularly, to air flow sensin arrangements for use in vacuum cleaners.
In vacuum cleaners, it is particularly important to maintain a predetermined minimum air flow level in order to assure that a vacuum cleaner is performing effectively. A full filter bag condition and/or a clogged hose condition in a vacuum cleaner impedes air flow through the cleaner and makes the cleaner ineffective for cleaning. Thus, it is desirable to provide an air flow sensing arrangement for informing an operator of a cleaner air flow problem so that the operator can take corrective action such as, for example, installing a clean filter bag or increasing motor power where an adjustable power control is available.
In order to provide a simple and economical air flow sensing arrangement to provide an indication of a low flow condition in a vacuum cleaner, it is generally desirable to provide a sensing element to sense only a portion of the total air flow so as to provide an indication of total air flow within the vacuum cleaner. However, vacuum cleaners have air flowing in a multitude of paths therein which may vary from unit to unit depending on the geometry of the cleaners. Thus, a sensing arrangement which may be suitable for one cleaner may not provide the desired accuracy in another cleaner because the sensing arrangement may be sensing a different proportion of the total cleaner air flow. A calibration provision could be provided but this generally adds complexity to a sensing arrangement and requires a calibration step in the vacuum cleaner fabrication process. Therefore, it would be advantageous to develop a simple and economical arrangement for sensing air flow conditions in a vacuum cleaner wherein a consistent proportion of the total air flow is sensed to provide an accurate and reliable indication of a predetermined total air flow without requiring calibration.
Further, vacuum cleaners often have very limited space available for accommodating an air flow sensing arrangement. Therefore, elaborate flow sensing arrangements are often not desirable from a space standpoint as well as from a cost standpoint. Thus, it would be advantageous to develop a flow sensing arrangement which could be easily integrated within available space and that could assure that a consistent proportion of total air is sensed to provide an accurate indication of a predetermined total air flow.
Still further, it would be desirable to provide such an improved air flow sensing arrangement with an accurate and reliable means of providing a remote indication of a predetermined flow condition. Air flow sensing arrangements often utilize the sensor itself for indication via a transparent window and/or some type of flag or indicator mechanically actuated by the sensor. However, such arrangements are often limited in mounting flexibility and/or visual indicating capability. Thus, it would be advantageous to provide an electrical switching arrangement which can provide reliable switching in a vacuum cleaner environment to provide a remote indication of a predetermined flow condition.